New designer drug alpha-pyrrolidinovalerophenone (PVP): studies on its metabolism and toxicological detection in rat urine using gas chromatographic/mass spectrometric techniques

In Vitro and In Vivo Toxicometabolomics of the Synthetic Cathinone PCYP Studied by Means of LC-HRMS/MS

Synthetic cathinones are one important group amongst new psychoactive substances (NPS) and limited information is available regarding their toxicokinetics and -dynamics. Over the past few years, nontargeted toxicometabolomics has been increasingly used to study compound-related effects of NPS to identify important exogenous and endogenous biomarkers. In this study, the effects of the synthetic cathinone PCYP (2-cyclohexyl-1-phenyl-2-(1-pyrrolidinyl)-ethanone) on in vitro and in vivo metabolomes were investigated. Pooled human-liver microsomes and blood and urine of male Wistar rats were used to generate in vitro and in vivo data, respectively. Samples were analyzed by liquid chromatography and high-resolution mass spectrometry using an untargeted metabolomics workflow. Statistical evaluation was performed using univariate and multivariate statistics. In total, sixteen phase I and one phase II metabolite of PCYP could be identified as exogenous biomarkers. Five endogenous biomarkers (e.g., adenosine and metabolites of tryptophan metabolism) related to PCYP intake could be identified in rat samples. The present data on the exogenous biomarker of PCYP are crucial for setting up analytical screening procedures. The data on the endogenous biomarker are important for further studies to better understand the physiological changes associated with cathinone abuse but may also serve in the future as additional markers for an intake.

An updated review on synthetic cathinones

Cathinone, the main psychoactive compound found in the plant Catha edulis Forsk. (khat), is a β-keto analogue of amphetamine, sharing not only the phenethylamine structure, but also the amphetamine-like stimulant effects. Synthetic cathinones are derivatives of the naturally occurring cathinone that largely entered the recreational drug market at the end of 2000s. The former "legal status", impressive marketing strategies and their commercial availability, either in the so-called "smartshops" or via the Internet, prompted their large spread, contributing to their increasing popularity in the following years. As their popularity increased, the risks posed for public health became clear, with several reports of intoxications and deaths involving these substances appearing both in the social media and scientific literature. The regulatory measures introduced thereafter to halt these trending drugs of abuse have proved to be of low impact, as a continuous emergence of new non-controlled derivatives keep appearing to replace those prohibited. Users resort to synthetic cathinones due to their psychostimulant properties but are often unaware of the dangers they may incur when using these substances. Therefore, studies aimed at unveiling the pharmacological and toxicological properties of these substances are imperative, as they will provide increased expertise to the clinicians that face this problem on a daily basis. The present work provides a comprehensive review on history and legal status, chemistry, pharmacokinetics, pharmacodynamics, adverse effects and lethality in humans, as well as on the current knowledge of the neurotoxic mechanisms of synthetic cathinones.

Novel Phenethylamines and Their Potential Interactions With Prescription Drugs: A Systematic Critical Review

BACKGROUND

The novel phenethylamines 4-fluoroamphetamine (4-FA) and 2,5-dimethoxy-4-bromophenethylamine (2C-B) fall in the top 10 most used new psychoactive substances (NPSs) among high-risk substance users. Various phenethylamines and NPS are also highly used in populations with mental disorders, depression, or attention deficit hyperactivity disorder (ADHD). Moreover, NPS use is highly prevalent among men and women with risky sexual behavior. Considering these specific populations and their frequent concurrent use of drugs, such as antidepressants, ADHD medication, and antiretrovirals, reports on potential interactions between these drugs, and phenethylamines 4-FA and 2C-B, were reviewed.

METHODS

The authors performed a systematic literature review on 4-FA and 2C-B interactions with antidepressants (citalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, duloxetine, bupropion, venlafaxine, phenelzine, moclobemide, and tranylcypromine), ADHD medications (atomoxetine, dexamphetamine, methylphenidate, and modafinil), and antiretrovirals.

RESULTS

Limited literature exists on the pharmacokinetics and drug-drug interactions of 2C-B and 4-FA. Only one case report indicated a possible interaction between 4-FA and ADHD medication. Although pharmacokinetic interactions between 4-FA and prescription drugs remain speculative, their pharmacodynamic points toward interactions between 4-FA and ADHD medication and antidepressants. The pharmacokinetic and pharmacodynamic profile of 2C-B also points toward such interactions, between 2C-B and prescription drugs such as antidepressants and ADHD medication.

CONCLUSIONS

A drug-drug (phenethylamine-prescription drug) interaction potential is anticipated, mainly involving monoamine oxidases for 2C-B and 4-FA, with monoamine transporters being more specific to 4-FA.

Pyrrolidinyl Synthetic Cathinones α-PHP and 4F-α-PVP Metabolite Profiling Using Human Hepatocyte Incubations

For more than ten years, new synthetic cathinones (SCs) mimicking the effects of controlled cocaine-like stimulants have flooded the illegal drug market, causing numerous intoxications and fatalities. There are often no data on the pharmacokinetics of these substances when they first emerge onto the market. However, the detection of SC metabolites is often critical in order to prove consumption in clinical and forensic settings. In this research, the metabolite profile of two pyrrolidinyl SCs, α-pyrrolidinohexaphenone (α-PHP) and 4''-fluoro-α-pyrrolidinovalerophenone (4F-α-PVP), were characterized to identify optimal intake markers. Experiments were conducted using pooled human hepatocyte incubations followed by liquid chromatography-high-resolution tandem mass spectrometry and data-mining software. We suggest α-PHP dihydroxy-pyrrolidinyl, α-PHP hexanol, α-PHP 2'-keto-pyrrolidinyl-hexanol, and α-PHP 2'-keto-pyrrolidinyl as markers of α-PHP use, and 4F-α-PVP dihydroxy-pyrrolidinyl, 4F-α-PVP hexanol, 4F-α-PVP 2'-keto-pyrrolidinyl-hexanol, and 4F-α-PVP 2'-keto-pyrrolidinyl as markers of 4F-α-PVP use. These results represent the first data available on 4F-α-PVP metabolism. The metabolic fate of α-PHP was previously studied using human liver microsomes and urine samples from α-PHP users. We identified an additional major metabolite (α-PHP dihydroxy-pyrrolidinyl) that might be crucial for documenting exposure to α-PHP. Further experiments with suitable analytical standards, which are yet to be synthesized, and authentic specimens should be conducted to confirm these results.

Synthetic drugs of abuse

Synthetic drugs of abuse contain various psychoactive substances. These substances have recently emerged as novel drugs of abuse in public; thus, they are known as novel psychoactive substances (NPS). As these compounds are artificially synthesized in a laboratory, they are also called designer drugs. Synthetic cannabinoids and synthetic cathinones are the two primary classes of NPS or designer drugs. Synthetic cannabinoids, also known as "K2" or "Spice," are potent agonists of the cannabinoid receptors. Synthetic cathinones, known as "Bath salts," are beta-keto amphetamine derivatives. These compounds can cause severe intoxication, including overdose deaths. NPS are accessible locally and online. NPS are scheduled in the US and other countries, but the underground chemists keep modifying the chemical structure of these compounds to avoid legal regulation; thus, these compounds have been evolving rapidly. These drugs are not detectable by traditional drug screening, and thus, these substances are mainly abused by young individuals and others who wish to avoid drug detection. These compounds are analyzed primarily by mass spectrometry.

Flakka: New Dangerous Synthetic Cathinone on the Drug Scene

New psychoactive substances are being used as drugs and appear to be quite popular nowadays. Thanks to their specific properties, these drugs create inimitable experiences for intoxicated people. Synthetic cathinones are the most common compounds in these new drugs. Among them, α-pyrrolidopentadione (α-PVP), or “Flakka” (street name), is one of the most famous cathinone-designed drugs. Similar to other synthetic cathinone drugs, α-PVP can effectively inhibit norepinephrine and dopamine transmitters. The adverse reactions of α-PVP mainly include mania, tachycardia, and hallucinations. An increasing number of people are being admitted to emergency wards due to the consequences of their use. This work mainly summarizes the history, synthesis, pharmacology, toxicology, structure–activity relationship, metabolism, clinical process and health risks, poisoning and death, forensic toxicology, and legal status of α-PVP. We hope this review will help bring more attention to the exploration of this substance in order to raise awareness of its negative impacts on humans.

MASS SPECTROMETRY ANALYSIS OF DRUGS OF ABUSE: CHALLENGES AND EMERGING STRATEGIES

Mass spectrometry has been the "gold standard" for drugs of abuse (DoA) analysis for many decades because of the selectivity and sensitivity it affords. Recent progress in all aspects of mass spectrometry has seen significant developments in the field of DoA analysis. Mass spectrometry is particularly well suited to address the rapidly proliferating number of very high potency, novel psychoactive substances that are causing an alarming number of fatalities worldwide. This review surveys advancements in the areas of sample preparation, gas and liquid chromatography-mass spectrometry, as well as the rapidly emerging field of ambient ionization mass spectrometry. We have predominantly targeted literature progress over the past ten years and present our outlook for the future. © 2020 Periodicals, Inc. Mass Spec Rev.

Determination of synthetic cathinone α-pyrrolidinovalero-phenone and its metabolite in urine using solid-phase extraction and gas chromatography-mass spectrometry

RATIONALE

The presence of α-pyrrolidinovalerophenone (α-PVP) and its metabolites in urine is evidence of the administration of α-PVP. A toxicological challenge is that the metabolites of α-PVP exhibit amphoteric properties, which make them unsuitable for detection using gas chromatography-mass spectrometry (GC/MS). In the study reported, proper derivatization and sample extraction were essential for improving the sensitivity for GC/MS analysis.

METHODS

An automated solid-phase extraction (SPE) method has been developed and optimized. The derivatization efficiency was tested using longer reaction time and the addition of polar pyridine into a mixture of N,O-bis(trimethylsilyl)trifluoroacetamide (BSTFA) with 1% trimethylchlorosilane. Method validation, including linearity, limit of detection, precision, accuracy, and recovery, was evaluated using automatic SPE and GC/MS.

RESULTS

The results suggested that adding pyridine to BSTFA (1:1, v/v) significantly improved derivatization efficiency and precision. After optimization, the linear range was from 25 to 1000 ng mL^-1 with R²  > 0.9950. The limit of detection was 5 ng mL^-1 for α-PVP and 25 ng mL^-1 for OH-α-PVP. The recovery for SPE was over 88%. The inter-day and intra-day precisions were less than 15%. A forensic sample has been found containing α-PVP (67.3 ng mL^-1 ) and OH-α-PVP (560.2 ng mL^-1 ).

CONCLUSIONS

This study is the first to validate an auto-SPE-GC/MS method for the quantification and qualification of α-PVP and OH-α-PVP in urine. We have successfully improved the derivatization efficiency and developed a sensitive and semi-automatic approach. This approach is desirable for the detection of synthetic cathinone at trace levels in biological samples.

[The use of extractive freezing-out at the stage of preliminary preparation of bioprobes in GC-MS chemico-toxicological analysis]

The authors propose a new express method of low-temperature sample preparation based on the use of extractive freezing-out combined with a sample centrifugation as a stage of a preliminary preparation of a biological object (cadaveric liver, kidneys). The method made it possible to minimize sufficiently the so-called chemical noise of endogenous coextractive substances and to improve sufficiently the conditions of the GC-MS method.

Synthetic cathinones: an evolving class of new psychoactive substances

Synthetic cathinones (SCat) are amphetamine-like psychostimulants that emerged onto drug markets as "legal" alternatives to illicit drugs such as ecstasy, cocaine, and amphetamines. Usually they are sold as "bath salts," "plant food," or "research chemicals," and rapidly gained popularity amongst drugs users due to their potency, low cost, and availability. In addition, internet drug sales have been replacing the old way of supplying drugs of abuse, contributing to their rapid spread. Despite the legislative efforts to control SCat, new derivatives continue to emerge on the recreational drugs market and their abuse still represents a serious public health issue. To date, about 150 SCat have been identified on the clandestine drugs market, which are one of the largest groups of new psychoactive substances (NPS) monitored by the United Nations Office on Drugs and Crime and the European Monitoring Center for Drugs and Drug Addiction. Similar to the classical stimulants, SCat affect the levels of catecholamines in the central nervous system, which results in their psychological, behavioral and toxic effects. Generally, the effects of SCat greatly differ from drug to drug and relatively little information is available about their pharmacology. The present work provides a review on the development of SCat as substances of abuse, current patterns of abuse and their legal status, chemical classification, known mechanisms of action, and their toxicological effects.

DARK Classics in Chemical Neuroscience: α-Pyrrolidinovalerophenone ("Flakka")

Flakka (alpha-pyrrolidinovalerophenone, α-PVP) is a new psychoactive substance, chemically close to cathinone, the primary psychoactive alkaloid of khat ( Catha edulis). Like other synthetic cathinones, α-PVP is a potent inhibitor of the dopamine and norepinephrine transporters. Its robust clinical effects include hallucinations, arousal, aggression/violence, and euphoria. In animal models, α-PVP evokes hyperlocomotion and aberrant/stereotypic behaviors. Here, we discuss the history, synthesis, pharmacological mechanisms, metabolism, abuse potential, and societal impact of α-PVP. Today, α-PVP is a tightly controlled substance, currently banned in the United States and other countries worldwide. However, the growing abuse and complex central nervous system (CNS) effects of α-PVP remain poorly understood, necessitating further pharmacological and pharmacogenetic studies of this drug. Its interesting pharmacological profile (co-inhibition of dopamine and norepinephrine, but not serotonin, transporters) also calls for further studies of α-PVP in animal models, to dissect serotonergic from other monoaminergic mechanisms of action of drugs of abuse. Finally, screening α-PVP and related compounds in vivo may foster discovery of new CNS drugs, including developing novel CNS drugs and identifying their molecular targets.

Comparative study on the metabolism of the ergot alkaloids ergocristine, ergocryptine, ergotamine, and ergovaline in equine and human S9 fractions and equine liver preparations

1. Ergopeptine alkaloids like ergovaline and ergotamine are suspected to be associated with fescue toxicosis and ergotism in horses. Information on the metabolism of ergot alkaloids is scarce, especially in horses, but needed for toxicological analysis of these drugs in urine/feces of affected horses. The aim of this study was to investigate the metabolism of ergovaline, ergotamine, ergocristine, and ergocryptine in horses and comparison to humans. 2. Supernatants of alkaloid incubations with equine and human liver S9 fractions were analyzed by reversed-phase liquid-chromatography coupled to high-resolution tandem mass spectrometry with full scan and MS² acquisition. Metabolite structures were postulated based on their MS² spectra in comparison to those of the parent alkaloids. All compounds were extensively metabolized yielding nor-, N-oxide, hydroxy and dihydro-diole metabolites with largely overlapping patterns in equine and human liver S9 fractions. However, some metabolic steps e.g. the formation of 8'-hydroxy metabolites were unique for human metabolism, while formation of the 13/14-hydroxy and 13,14-dihydro-diol metabolites were unique for equine metabolism. Incubations with equine whole liver preparations yielded less metabolites than the S9 fractions. 3. The acquired data can be used to develop metabolite-based screenings for these alkaloids, which will likely extend their detection windows in urine/feces from affected horses.

"Marvin, the Paranoid Android": The Case of an Alpha-PVP User in the Expanding Galaxy of NPS

Alpha-PVP can be defined as a novel psychoactive substance (NPS)-more specifically, a novel synthetic cathinone with unpredictable stimulant effects in humans. "Marvin" arrived at a Dual Diagnosis Unit at Parco dei Tigli, Italy. He underwent a 30-day rehabilitation program to overcome his problematic Alpha-PVP use as a psychonaut. We conducted an online search to understand the properties of Alpha-PVP and its presence in scientific literature, reviewing official reports and the online drug market (e.g., fora, webpages). In the Dual Diagnosis Unit, Marvin completed the 30-day rehabilitation program that included assessments and group and individual cognitive behavioral therapy. Alpha-PVP is a synthetic cathinone with stimulant properties, available in the online market but with unpredictable effects in humans. The present case reports an important risk of psychosis in a psychonaut patient who arrived and declared its intense use before admission to our Unit. This article describes the psychopathological effects of the novel compound Alpha-PVP in a psychonaut patient. Patients attending clinics that have used Alpha-PVP pose a new challenge for traditional services of mental health and addiction.

The synthetic cathinone α-pyrrolidinovalerophenone (α-PVP): pharmacokinetic and pharmacodynamic clinical and forensic aspects

New psychoactive substances (NPS), often referred as 'legal highs' or 'designer drugs', are derivatives and analogs of existing psychoactive drugs that are introduced in the recreational market to circumvent existing legislation on drugs of abuse. This work aims to review the state-of-the-art regarding chemical, molecular pharmacology, and in vitro and in vivo data on toxicokinetics of the potent synthetic cathinone α-pyrrolidinovalerophenone (α-PVP or flakka or zombie drug). Chemical, pharmacological, toxicological, and clinical effects of α-PVP were searched in PubMed (U.S. National Library of Medicine) and governmental websites without limitation of the period. α-PVP is a wide spread and easy to get special type of synthetic cathinone with seemingly powerful cocaine-like stimulant effects, high brain penetration, high liability for abuse and with increased risk of adverse effects such as tachycardia, agitation, hypertension, hallucinations, delirium, mydriasis, self-injury, aggressive behavior, and suicidal ideations. α-PVP undergoes extensive metabolism via different pathways and the α-PVP itself or its metabolites β-hydroxy-α-PVP and α-PVP lactam represent the main targets for toxicological analysis in urine. There is a limited knowledge regarding the short- and long-term effects of α-PVP and metabolites, and pharmacogenetic influence, hence further clinical and forensic toxicological studies are required. Moreover, since α-PVP cannot be detected with classic routine analysis procedures, statements on the frequency of their consumption cannot be made.

[The determination of pyrovaleron in the urine by gas chromatography in the combination with the method of extractive chilling-out and centrifugation]

The express-method for the determination of pyrovaleron in the urine based on the combination with the method of extractive freezing-out and centrifugation of the samples as the preliminary stage of the preparation of a biological object for the analysis. The identification and quantitative determination of the substance of interest were performed using gas chromatography with nitrogen-selective detection. The preparation of the samples was carried out as a single-step procedure no longer than 30 min in duration. The limit of alpha-pyrovaleron detection in the urine was estimated at 1 mcg/ml. Its concentration after extraction from the urine increased by a factor of more than nine.

Toxicological investigation of forensic cases related to the designer drug 3,4-methylenedioxypyrovalerone (MDPV): Detection, quantification and studies on human metabolism by GC-MS

3,4-methylenedioxypyrovalerone (MDPV) is a synthetic cathinone belonging to the class of α-pyrrolidinophenones that become increasingly popular as a designer psychostimulant. Here, we report a comprehensive collection of MDPV exposure with quantitative serum level confirmation in Germany. During the years 2014-2016, we could proof consumption of MDPV in 23 cases where urine and blood samples were submitted to our laboratory by the police of Lower Saxony. Most of the samples underwent systematic toxicological analysis by gas chromatography-mass spectrometry (GC-MS), where MDPV could be detected in urine and/or serum samples. The determined concentrations of MDPV in serum showed a high variability, ranging from traces (<10ng/mL) up to 576ng/mL with a mean concentration of 118ng/mL and median of 47ng/mL. The majority of MDPV users were men (87%) and the age ranged from 23 to 49 years (mean 35.9, median 37 years). For most of the analytically confirmed MDPV cases we could prove co-consumption of other psychotropic drugs with frequent occurrence of opiates and cannabinoids in 22% of the cases, followed by benzodiazepines and cocaine in 17%. Analysis of urine samples by GC-MS disclosed the presence of MDPV and its metabolites 2'-oxo-MDPV, demethylenyl-MDPV, demethylenyl-methyl-MDPV, demethylenyl-oxo-MDPV, demethylenyl-methyl-oxo-MDPV and demethylenyl-methyl-N,N-bisdealkyl-MDPV. The metabolite pattern substantiates previous suggestions for principle metabolic pathways of MDPV in humans.

The Toxicology of New Psychoactive Substances: Synthetic Cathinones and Phenylethylamines

BACKGROUND

New psychoactive substances (NPSs) are substitutes for classical drugs of abuse and there are now compounds available from all groups of classical drugs of abuse. During 2014, the number of synthetic cathinones increased dramatically and, together with phenylethylamines, they dominate the NPS markets in the European Union. In total, 31 cathinones and 9 phenylethylamines were encountered in 2014. The aim of this article was to summarize the existing knowledge about the basic pharmacology, metabolism, and human toxicology of relevant synthetic cathinones and phenylethylamines. Compared with existing reviews, we have also compiled the existing case reports from both fatal and nonfatal intoxications.

METHODS

We performed a comprehensive literature search using bibliographic databases PubMed and Web of Science, complemented with Google Scholar. The focus of the literature search was on original articles, case reports, and previously published review articles published in 2014 or earlier.

RESULTS

The rapid increase of NPSs is a growing concern and sets new challenges not only for societies in drug prevention and legislation but also in clinical and forensic toxicology. In vivo and in vitro studies have demonstrated that the pharmacodynamic profile of cathinones is similar to that of other psychomotor stimulants. Metabolism studies show that cathinones and phenylethylamines are extensively metabolized; however, the parent compound is usually detectable in human urine. In vitro studies have shown that many cathinones and phenylethylamines are metabolized by CYP2D6 enzymes. This indicates that these drugs may have many possible drug-drug interactions and that genetic polymorphism may influence their toxicity. However, the clinical and toxicological relevance of CYP2D6 in adverse effects of cathinones and phenylethylamines is questionable, because these compounds are metabolized by other enzymes as well. The toxidromes commonly encountered after ingestion of cathinones and phenylethylamines are mainly of sympathomimetic and hallucinogenic character with a risk of excited delirium and life-threatening cardiovascular effects.

CONCLUSIONS

The acute and chronic toxicity of many NPSs is unknown or very sparsely investigated. There is a need for evidence-based-treatment recommendations for acute intoxications and a demand for new strategies to analyze these compounds in clinical and forensic cases.

Synthetic cathinone pharmacokinetics, analytical methods, and toxicological findings from human performance and postmortem cases

Synthetic cathinones are commonly abused novel psychoactive substances (NPS). We present a comprehensive systematic review addressing in vitro and in vivo synthetic cathinone pharmacokinetics, analytical methods for detection and quantification in biological matrices, and toxicological findings from human performance and postmortem toxicology cases. Few preclinical administration studies examined synthetic cathinone pharmacokinetic profiles (absorption, distribution, metabolism, and excretion), and only one investigated metabolite pharmacokinetics. Synthetic cathinone metabolic profiling studies, primarily with human liver microsomes, elucidated metabolite structures and identified suitable biomarkers to extend detection windows beyond those provided by parent compounds. Generally, cathinone derivatives underwent ketone reduction, carbonylation of the pyrrolidine ring, and oxidative reactions, with phase II metabolites also detected. Reliable analytical methods are necessary for cathinone identification in biological matrices to document intake and link adverse events to specific compounds and concentrations. NPS analytical methods are constrained in their ability to detect new emerging synthetic cathinones due to limited commercially available reference standards and continuous development of new analogs. Immunoassay screening methods are especially affected, but also gas-chromatography and liquid-chromatography mass spectrometry confirmation methods. Non-targeted high-resolution-mass spectrometry screening methods are advantageous, as they allow for retrospective data analysis and easier addition of new synthetic cathinones to existing methods. Lack of controlled administration studies in humans complicate interpretation of synthetic cathinones in biological matrices, as dosing information is typically unknown. Furthermore, antemortem and postmortem concentrations often overlap and the presence of other psychoactive substances are typically found in combination with cathinones derivatives, further confounding result interpretation.

First metabolic profile of PV8, a novel synthetic cathinone, in human hepatocytes and urine by high-resolution mass spectrometry

Novel psychoactive substances (NPS) are ever changing on the drug market, making it difficult for toxicology laboratory methods to stay current with so many new drugs. Recently, PV8, a synthetic pyrrolidinophenone, was detected in seized products in Japan (2013), The Netherlands (2014), and Germany (2014). There are no controlled PV8 administration studies, and no pharmacodynamic and pharmacokinetic data. The objective was to determine PV8's metabolic stability in human liver microsome (HLM) incubation and its metabolism following human hepatocyte incubation and high-resolution mass spectrometry (HRMS) with a Thermo Scientific Q-Exactive. Data were acquired with a full-scan data-dependent mass spectrometry method. Scans were thoroughly data mined with different data processing algorithms and analyzed in WebMetaBase. PV8 exhibited a relatively short 28.8 min half-life, with an intrinsic 24.2 μL/min/mg microsomal clearance. This compound is predicted to be an intermediate clearance drug with an estimated human 22.7 mL/min/kg hepatic clearance. Metabolic pathways identified in vitro included: hydroxylation, ketone reduction, carboxylation, N-dealkylation, iminium formation, dehydrogenation, N-oxidation, and carbonylation. The top three in vitro metabolic pathways were di-hydroxylation > ketone reduction > γ-lactam formation. Authentic urine specimen analyses revealed the top three metabolic pathways were aliphatic hydroxylation > ketone reduction + aliphatic hydroxylation > aliphatic carboxylation, although the most prominent peak was parent PV8. These data provide useful urinary metabolite targets (aliphatic hydroxylation, aliphatic hydroxylation + ketone reduction, aliphatic carboxylation, and di-hydroxylation) for forensic and clinical testing, and focus reference standard companies' synthetic efforts to provide commercially available standards needed for PV8 biological specimen testing. Graphical Abstract Top four PV8 metabolites identified in vitro. Biotransformations highlighted in blue. Markush structures presented when exact location of biotransformation is unknown.

Neurobiology of 3,4-methylenedioxypyrovalerone (MDPV) and α-pyrrolidinovalerophenone (α-PVP)

Synthetic cathinones are analogs of cathinone or β-ketoamphetamine - the major psychostimulant component of the shrub Catha edulis or khat. Cathinone analogs - though not termed as such - have been known for >100 years, but confusing chemical nomenclature often made the topic difficult to appreciate. In addition, many of the early analogs were prepared as synthetic precursors for the development of various other agents, and relatively few were pharmacologically evaluated. Cathinone is a close structural relative of amphetamine. Today, certain cathinone derivatives, synthetic cathinones, are known to produce central stimulant actions and represent a "new" class of drugs of abuse. Depending upon the nature of their terminal amine, α substituent, and aryl substituents, they seem to produce their effects via release or reuptake of various neurotansmitters including dopamine norepinephreine and/or serotonin. Two of the newest and most prominent members of the class are MDPV and its parent α-PVP ("flakka"). Both have been encountered on their own and in what might be constituents of what has been termed by a variety of names including psychoactive "bath salts". Here, we describe the nomenclature of synthetic cathinones, the mechanism(s) of action of MDPV and α-PVP, and their structure-activity relationships. In order to assist in forensic studies, and to identify novel substances requiring future pharmacological evaluation, the metabolism of these agents is also described. Finally, the preclinical behavioral actions of these two agents in a variety of behavioral assays, including rodent locomotor assays, self-administration studies, intracranial self-stimulation, conditioned place preference, and drug discrimination, is summarized. The results of these studies with MDPV and α-PVP are consistent with their acting as potent cocaine-like central stimulants with abuse liability.

Prevalence of Rhabdomyolysis in Sympathomimetic Toxicity: a Comparison of Stimulants

Synthetic cathinones have emerged as popular drugs of abuse and produce sympathomimetic toxicity. It is unknown if rhabdomyolysis occurs more frequently following the use of synthetic cathinones compared to other stimulants. This retrospective study sought to determine the prevalence of rhabdomyolysis in patients with sympathomimetic toxicity and compare rates among patients using specific agents. Patients greater than 14 years of age with sympathomimetic toxicity and detection of a stimulant agent in urine via gas chromatography-mass spectroscopy (GC-MS) were included. Patients were excluded if clinical sympathomimetic toxicity was not present, a serum creatine kinase (CK) was not measured, or urine GC-MS was not performed. Rhabdomyolysis and severe rhabdomyolysis were defined as CK > 1000 and 10,000 IU/L, respectively. Prevalence of rhabdomyolysis and severe rhabdomyolysis were reported. Logistic regression was performed to determine the relative effect in single-agent exposures of a synthetic cathinone compared to other sympathomimetics on rhabdomyolysis. A secondary outcome, a composite endpoint defined as need for mechanical ventilation, renal replacement therapy, development of compartment syndrome, or death, was also analyzed. One hundred two subjects met inclusion criteria; median age (IQR) was 32 (25-42) years with a range of 14-65 years; 74 % were male. Rhabdomyolysis occurred in 42 % (43/102) of subjects. Patients whose sympathomimetic toxicity could be ascribed to a single agent were considered for further statistical analysis and placed into four groups: methamphetamine (n = 55), synthetic cathinone (n = 19), cocaine (n = 9), and other sympathomimetic (n = 6). In 89 subjects with single stimulant exposure, the prevalence of rhabdomyolysis was as follows: synthetic cathinone, 12/19 (63 %); methamphetamine, 22/55 (40 %); cocaine, 3/9 (33 %); and other single agent, 0/6 (0 %). The occurrence of severe rhabdomyolysis (CK > 10,000 IU/L) for each of the four groups was synthetic cathinone with 5/19 (26 %), methamphetamine with 2/55 (3.6 %), cocaine with 1/9 (11 %), and other with 0/6 (0 %). Median maximal CK (range) by groups was as follows: synthetic cathinone, 2638 (62-350,000+) IU/L; methamphetamine, 665 (61-50,233) IU/L; cocaine, 276 (87-25,614) IU/L; and other, 142 (51-816) IU/L. A statistically significant difference (p = 0.004) was found when comparing maximal CK among the four groups. Exposure to a synthetic cathinone compared with other sympathomimetics was associated with increased risk of developing rhabdomyolysis and severe rhabdomyolysis with odds ratios of 3.09 and 7.98, respectively. In this cohort of patients with sympathomimetic toxicity, 42 % developed rhabdomyolysis. Synthetic cathinones were associated with an increased risk of rhabdomyolysis and severe rhabdomyolysis compared with other stimulants.

Suicide attempt with a mix of synthetic cannabinoids and synthetic cathinones: Case report of non-fatal intoxication with AB-CHMINACA, AB-FUBINACA, alpha-PHP, alpha-PVP and 4-CMC

We report on a case of intoxication with a mix of new psychoactive substances. A 38-year-old male was brought to the emergency department (ED) following the ingestion of an unknown drug in a suicide attempt. During the transport, he became progressively more somnolent and unresponsive to painful stimuli. Urine and stomach content were collected on admission to be screened for drugs of abuse and medicinal drugs. After admission, the patient's next of kin presented five small grip seal plastic bags containing different powders/crystals, and they were sent for analysis along with urine and stomach content to the toxicology laboratory. An easy and rapid sample preparation technique was applied for the extraction of urine and stomach content. Samples were extracted with liquid-liquid extraction (LLE) technique and analysed using gas chromatography-mass spectrometry (GC-MS). A small amount of powder material from the bags was diluted in methanol and injected directly into the GC-MS instrument. Obtained spectra (EI) were evaluated against SWGDRUG library. Five different designer drugs were identified in the powder material, including synthetic cannabinoids (AB-CHMINACA, AB-FUBINACA) and synthetic cathinones (alpha-PHP, alpha-PVP and 4-CMC). With the exception of 4-CMC, all of these substances were also detected in the stomach content along with the prescription drugs. This is the first time that a positive identification of these five drugs has been made by a clinical laboratory in Slovenia.

In vitro, in vivo and in silico metabolic profiling of α-pyrrolidinopentiothiophenone, a novel thiophene stimulant

BACKGROUND

Little or no pharmacological or toxicological data are available for novel psychoactive substances when they first emerge, making their identification and interpretation in biological matrices challenging.

MATERIALS & METHODS

A new synthetic cathinone, α-pyrrolidinopentiothiophenone (α-PVT), was incubated with hepatocytes and samples were analyzed using liquid chromatography coupled to a Q Exactive™ Orbitrap mass spectrometer. Authentic urine specimens from suspected α-PVT cases were also analyzed. Scans were data mined with Compound Discoverer™ for identification and structural elucidation of metabolites.

RESULTS/CONCLUSION

Seven α-PVT metabolites were identified in hepatocyte incubations, and in the authentic urine samples, also with an additional monohydroxylated product and a glucuronide of low intensity. α-PVT dihydroxypyrrolidinyl, α-PVT 2-ketopyrrolidinyl, α-PVT hydroxythiophenyl and α-PVT thiophenol had the most intense in vivo signals.

4-Methoxy-α-PVP: in silico prediction, metabolic stability, and metabolite identification by human hepatocyte incubation and high-resolution mass spectrometry

Novel psychoactive substances are continuously developed to circumvent legislative and regulatory efforts. A new synthetic cathinone, 4-methoxy-α-PVP, was identified for the first time in illegal products; however, the metabolism of this compound is not known. Complete metabolic profiles are needed for these novel psychoactive substances to enable identification of their intake and to link adverse effects to the causative agent. This study assessed 4-methoxy-α-PVP metabolic stability with human liver microsomes (HLMs) and identified its metabolites after HLM and hepatocyte incubations followed by high-resolution mass spectrometry (HRMS). A Thermo QExactive high-resolution mass spectrometer (HRMS) was used with full scan data-dependent mass spectrometry, with (1) and without (2) an inclusion list of predicted metabolite, and with full scan and all-ion fragmentation (3) to identify potential unexpected metabolites. In silico predictions were performed and compared to in vitro results. Scans were thoroughly mined with different data processing algorithms using WebMetabase (Molecular Discovery). 4-Methoxy-α-PVP exhibited a long half-life of 79.7 min in HLM, with an intrinsic clearance of 8.7 µL min⁻¹ mg⁻¹. In addition, this compound is predicted to be a low-clearance drug with an estimated human hepatic clearance of 8.2 mL min⁻¹ kg⁻¹. Eleven 4-methoxy-α-PVP metabolites were identified, generated by O-demethylation, hydroxylation, oxidation, ketone reduction, N-dealkylation, and glucuronidation. The most dominant metabolite in HLM and human hepatocyte samples was 4-hydroxy-α-PVP, also predicted as the #1 in silico metabolite, and is suggested to be a suitable analytical target in addition to the parent compound.

In vitro Phase I and Phase II metabolism of α-pyrrolidinovalerophenone (α-PVP), methylenedioxypyrovalerone (MDPV) and methedrone by human liver microsomes and human liver cytosol

The aim of the present study was to identify the in vitro Phase I and Phase II metabolites of three new psychoactive substances: α-pyrrolidinovalerophenone (α-PVP), methylenedioxypyrovalerone (MDPV), and methedrone, using human liver microsomes and human liver cytosol. Accurate-mass spectra of metabolites were obtained using liquid chromatography-quadrupole time-of-flight mass spectrometry. Six Phase I metabolites of α-PVP were identified, which were formed involving reduction, hydroxylation, and pyrrolidine ring opening reactions. The lactam compound was the major metabolite observed for α-PVP. Two glucuronidated metabolites of α-PVP, not reported in previous in vitro studies, were further identified. MDPV was transformed into 10 Phase I metabolites involving reduction, hydroxylation, and loss of the pyrrolidine ring. Also, six glucuronidated and two sulphated metabolites were detected. The major metabolite of MDPV was the catechol metabolite. Methedrone was transformed into five Phase I metabolites, involving N- and O-demethylation, hydroxylation, and reduction of the ketone group. Three metabolites of methedrone are reported for the first time. In addition, the contribution of individual human CYP enzymes in the formation of the detected metabolites was investigated.

Comprehensive review of the detection methods for synthetic cannabinoids and cathinones

A number of N-alkyl indole or indazole-3-carbonyl analogs, with modified chemical structures, are distributed throughout the world as synthetic cannabinoids. Like synthetic cannabinoids, cathinone analogs are also abused and cause serious problems worldwide. Acute deaths caused by overdoses of these drugs have been reported. Various analytical methods that can cope with the rapid changes in chemical structures are required for routine analysis and screening of these drugs in seized and biological materials for forensic and clinical purposes. Although many chromatographic methods to analyze each drug have been published, there are only a few articles summarizing these analytical methods. This review presents the various colorimetric detections, immunochemical assays, gas chromatographic-mass spectrometric methods, and liquid chromatographic-mass spectrometric methods proposed for the analysis of synthetic cannabinoids and cathinones.

Comprehensive review of the detection methods for synthetic cannabinoids and cathinones

A number of N-alkyl indole or indazole-3-carbonyl analogs, with modified chemical structures, are distributed throughout the world as synthetic cannabinoids. Like synthetic cannabinoids, cathinone analogs are also abused and cause serious problems worldwide. Acute deaths caused by overdoses of these drugs have been reported. Various analytical methods that can cope with the rapid changes in chemical structures are required for routine analysis and screening of these drugs in seized and biological materials for forensic and clinical purposes. Although many chromatographic methods to analyze each drug have been published, there are only a few articles summarizing these analytical methods. This review presents the various colorimetric detections, immunochemical assays, gas chromatographic-mass spectrometric methods, and liquid chromatographic-mass spectrometric methods proposed for the analysis of synthetic cannabinoids and cathinones.

Metabolism of the designer drug α-pyrrolidinobutiophenone (α-PBP) in humans: identification and quantification of the phase I metabolites in urine

Urinary phase I metabolites of α-pyrrolidinobutiophenone (α-PBP) in humans were investigated by analyzing urine specimens obtained from drug abusers. Unequivocal identification and accurate quantification of major metabolites were realized using gas chromatography-mass spectrometry and liquid chromatography-tandem mass spectrometry with newly synthesized authentic standards. Two major phase I metabolic pathways were revealed: (1) reduction of the ketone group to 1-phenyl-2-(pyrrolidin-1-yl)butan-1-ol (OH-α-PBP, diastereomers) partly followed by conjugation to its glucuronide and (2) oxidation at the 2″-position of the pyrrolidine ring to α-(2″-oxo-pyrrolidino)butiophenone (2″-oxo-α-PBP) via the putative intermediate α-(2″-hydroxypyrrolidino)butiophenone (2″-OH-α-PBP). Of the phase I metabolites retaining the structural characteristics of the parent drug, OH-α-PBP was the most abundant in all specimens examined. Comparison of the phase I metabolism of α-PBP and α-pyrrolidinovalerophenone (α-PVP) suggested a relationship between the aliphatic side chain length and the metabolic pathways in α-pyrrolidinophenones: the shorter aliphatic side chain (1) led to more extensive metabolism via reduction of the ketone group than via the oxidation at the 2″-position of the pyrrolidine ring and (2) influenced the isomeric ratio of a pair of diastereomers.

New recreational drug 1-phenyl-2-(1-pyrrolidinyl)-1-pentanone (alpha-PVP) activates central nervous system via dopaminergic neuron

1-phenyl-2-(1-pyrrolidinyl)-1-pentanone (α-PVP) is a new designer drug of the cathinone type. People who have taken drugs containing α-PVP or other synthetic cathinone reportedly lose consciousness, develop difficulty breathing, and at worst case, die. However, the mechanism underlying α-PVP-induced neurotoxicity is unknown. The objective of the present study was to investigate the effect of α-PVP on the central nervous system (CNS) and compare its neurotoxicity with that of methamphetamine (METH) in mice. Balb/c male mice (8 weeks old) were orally administered α-PVP (25 mg/kg) or METH (5 mg/kg). α-PVP induced a significant increase in locomotor activity, which occurred earlier than locomotor activity induced by METH. This increase was inhibited by the D1 receptor antagonist SCH23990 (50 µg/kg, i.p.) and the D2 receptor antagonist sulpiride (50 mg/kg, i.m.). The extracellular concentration of dopamine (DA) in the striatum, determined by in vivo microdialysis increased immediately after α-PVP administration. These results suggest that α-PVP stimulates DA release, causing an increase in locomotor activity, and that this stimulatory effect of α-PVP on CNS is mediated, at least in part, by the D1 and D2 receptors.

Testing for designer stimulants: metabolic profiles of 16 synthetic cathinones excreted free in human urine

The study of 34,561 urine specimens, submitted for designer stimulant testing between February 2011 and January 2013, provided an opportunity: to estimate the range of synthetic cathinones (SC) abused in the USA, to observe multiple examples of metabolic profiles for each drug in various stages of excretion in human urine, to evaluate the extent of metabolism of specific SC and to select metabolites or parent drugs for routine testing. Sixteen SC were found in random patient samples: buphedrone; butylone; 3,4-dimethylmethcathinone; ethcathinone; N-ethylbuphedrone; ethylone; flephedrone; mephedrone; 4-methylbuphedrone; 3,4-methylenedioxypyrovalerone (MDPV); 4-methyl-N-ethylcathinone; methylone; pentedrone; pentylone; α-pyrrolidinobutiophenone (PBP) and α-pyrrolidinopentiophenone (PVP). After liquid/liquid extraction and trifluoroacetylation, specimens were screened by gas chromatography-mass spectrometry (GC-MS) for drugs and metabolites excreted free in urine. Each SC exhibited a characteristic metabolic profile, as shown by multiple examples. Metabolites' structures were postulated on the basis of their mass spectra. A large group of SC appears to metabolize extensively by carbonyl reduction into respective substituted ephedrines and further by N-dealkylation into norephedrines. Abundant metabolites in this group are essential markers of the parent drug use. Unchanged drugs are far less abundant or not found at all. SC with methylenedioxy attachment to the aromatic ring, metabolize by carbonyl reduction to a much lesser extent and are best detected as such in free urine fraction. PBP and PVP can be detected either unchanged or as metabolites, resulting from pyrrolidine ring degradation into primary amine followed by carbonyl reduction. MDPV appears in urine as such with no apparent free metabolites.

Khat and synthetic cathinones: a review

For centuries, 'khat sessions' have played a key role in the social and cultural traditions among several communities around Saudi Arabia and most East African countries. The identification of cathinone as the main psychoactive compound of khat leaves, exhibiting amphetamine-like pharmacological properties, resulted in the synthesis of several derivatives structurally similar to this so-called natural amphetamine. Synthetic cathinones were primarily developed for therapeutic purposes, but promptly started being misused and extensively abused for their euphoric effects. In the mid-2000's, synthetic cathinones emerged in the recreational drug markets as legal alternatives ('legal highs') to amphetamine, 'ecstasy', or cocaine. Currently, they are sold as 'bath salts' or 'plant food', under ambiguous labels lacking information about their true contents. Cathinone derivatives are conveniently available online or at 'smartshops' and are much more affordable than the traditional illicit drugs. Despite the scarcity of scientific data on these 'legal highs', synthetic cathinones use became an increasingly popular practice worldwide. Additionally, criminalization of these derivatives is often useless since for each specific substance that gets legally controlled, one or more structurally modified analogs are introduced into the legal market. Chemically, these substances are structurally related to amphetamine. For this reason, cathinone derivatives share with this drug both central nervous system stimulating and sympathomimetic features. Reports of intoxication and deaths related to the use of 'bath salts' have been frequently described over the last years, and several attempts to apply a legislative control on synthetic cathinones have been made. However, further research on their pharmacological and toxicological properties is fully required in order to access the actual potential harm of synthetic cathinones to general public health. The present work provides a review on khat and synthetic cathinones, concerning their historical background, prevalence, patterns of use, legal status, chemistry, pharmacokinetics, pharmacodynamics, and their physiological and toxicological effects on animals and humans.

In silico and in vitro metabolism studies support identification of designer drugs in human urine by liquid chromatography/quadrupole-time-of-flight mass spectrometry

Human phase I metabolism of four designer drugs, 2-desoxypipradrol (2-DPMP), 3,4-dimethylmethcathinone (3,4-DMMC), α-pyrrolidinovalerophenone (α-PVP), and methiopropamine (MPA), was studied using in silico and in vitro metabolite prediction. The metabolites were identified in drug abusers’ urine samples using liquid chromatography/quadrupole-time-of-flight mass spectrometry (LC/Q-TOF/MS). The aim of the study was to evaluate the ability of the in silico and in vitro methods to generate the main urinary metabolites found in vivo. Meteor 14.0.0 software (Lhasa Limited) was used for in silico metabolite prediction, and in vitro metabolites were produced in human liver microsomes (HLMs). 2-DPMP was metabolized by hydroxylation, dehydrogenation, and oxidation, resulting in six phase I metabolites. Six metabolites were identified for 3,4-DMMC formed via N-demethylation, reduction, hydroxylation, and oxidation reactions. α-PVP was found to undergo reduction, hydroxylation, dehydrogenation, and oxidation reactions, as well as degradation of the pyrrolidine ring, and seven phase I metabolites were identified. For MPA, the nor-MPA metabolite was detected. Meteor software predicted the main human urinary phase I metabolites of 3,4-DMMC, α-PVP, and MPA and two of the four main metabolites of 2-DPMP. It assisted in the identification of the previously unreported metabolic reactions for α-PVP. Eight of the 12 most abundant in vivo phase I metabolites were detected in the in vitro HLM experiments. In vitro tests serve as material for exploitation of in silico data when an authentic urine sample is not available. In silico and in vitro designer drug metabolism studies with LC/Q-TOF/MS produced sufficient metabolic information to support identification of the parent compound in vivo.

Toxicity and death following recreational use of 2-pyrrolidino valerophenone

BACKGROUND

Consumption of substituted cathinones, frequently called 'legal highs' or 'designer drugs', is increasing in the European Union. In July 2012, the French Medicine Agency listed the substituted cathinone's chemical family as narcotic and psychotropic substances, to restrict their use and distribution. We present, here, the first documented cases of recreational use of 2-pyrrolidino valerophenone (PVP) associated with death for one patient, with post-mortem toxicological analysis.

CASE REPORTS

Two men purchased the legal high Energy-3 (NRG-3). It can be sold as laboratory reagent and is available from Internet. The oldest died of sudden cardiac arrest. The other experienced visual hallucinations and psychotic symptoms for 24 h. He also presented bilateral mydriasis, sinus tachycardia and rhabdomyolysis. He reported an occasional intranasal use of NRG-3. Analysis of the powder and blood and urine from both men revealed the presence of PVP.

DISCUSSION AND CONCLUSION

PVP belongs to the substituted cathinones chemical family. These cases highlight the need for emergency physicians, toxicologists and networks of toxicovigilance to control the use of these substances and their dangers, quickly identify cases of severe poisoning associated with the use of new drugs and to develop detection methods.

Emergence and properties of spice and bath salts: a medicinal chemistry perspective

Over the past five years the number of internet sites advertising "legal highs" has literally exploded, as have user reports of experiences (both pleasurable and frightening) with these substances and the number of emergency room visits by users. Although the majority of these "legal highs" have been described as bath salts and herbal extracts, most contain neither plant derived compounds nor components of personal hygiene products. So-called "bath salts" largely contain synthetic analogs of the natural compound Khat; spice-related materials, claimed to be "legal marijuana," are mostly synthetic analogs of cannabinoid receptor ligands that were developed as research tools. This review describes the emergence and properties of these two groups of "legal highs" from a medicinal chemist's perspective.